jmc

Let $x$ be the number of rows with 8 people. If we removed a person from each of these rows, then every row would contain 7 people. Therefore, $46-x$ must be divisible by 7.

Then $x\equiv 46\equiv 4(\mathrm{mod}7)$. The first few positive integers that satisfy this congruence are 4, 11, 18, and so on. However, each row contains at least 7 people. If there were 7 or more rows, then there would be at least $7\cdot 7=49$ people. We only have 46 people, so there must be at most six rows. Therefore, the number of rows with 8 people is $\boxed{4}$.